Filter or strainer for liquids



Jan. 4, 1949. P. L. BOUCHER 2,458,139

FILTER on STRAINAER ron mourns Filed Oct. 11, 1947 INVENTOR PERCIVAL .LIONEL BOUGHER PW W M K W ATTORNEYS Patented Jan. 4, 1949 FILTER OR STRAINER FOR LIQUIDS Percival Lionel Boucher. Troon, Scotland, assignor to Glenfield and Kennedy Limited, Kilmarnock, Scotland, a corporation of Great Britain and Northern Ireland Application October 11, 1947, Serial No. 779,274 In Great Britain October 15, 1946 3 Claims. 1

This invention relates to filters or strainers for liquids.

In filters employing a screen of Wire-cloth or other foraminous material of ultra-fine mesh, 1. e., having interstices of microscopic proportions arranged to be cleaned by jets of cleaning liquid, trouble is experienced in ensuring penetration of the interstices by the cleaning liquid on account of the surface tension of the liquid held in the meshes of the wire-cloth or other material. This surface tension is always present, but it is not appreciable in wire-cloth of wide mesh in which, in each interstice, the boundary supports of the contained lamina of liquid are sufficlently far apart to allow sumcient bending moment to be generated at the centre of the lamina by the impact of a particle of cleaning liquid to rupture the surface and allow the cleaning liquid to pass through. In a very small interstice the boundary supports of a contained lamina of liquid are so close together that sufficient bending moment to cause rupture of the surface cannot be generated by the impact of particles of cleaning liquid even when moving at high velocity. This is particularly true if the filter or strainer is made of stainless steel woven wire fabric.

In a filter according to the invention a foraminous sheet of ultra-fine mesh as aforesaid is interposed between foraminous sheets of Wirecloth or other material of wider mesh. Both sheets of wide mesh hold liquid in their interstices, but as the sheet of ultra-fine mesh is positioned between them, the sheet of ultra-fine mesh is immersed in liquid held between the sheets of wider mesh, Thereis thus no liquid surface existing in the microscopic interstices and surface tension is absent. Cleaning liquid can thus pass through with slight resistance.

The invention is applicable, for example, to filters of the type described in the specification of application No. 676,083 in which the screen is composed of exceptionally fine stainless steel wire fabric woven with straight warps and crimped wefts.

A practical embodiment of the invention is illustrated in the accompanying drawing in which i denotes a rotary screen carried by a spindle 2 supported in a bearing 3. 4 denotes a driving motor and 5 denotes a friction wheel geared to the motor 4 and bearing against the rim of the wheel I. 6 and 1 denote woven wire fabric sheets of relatively coarse mesh and 8 denotes a stainless steel woven wire fabric sheet of ultra-fine mesh, the several sheets being cut away to illustrate the mode of assembly. 9 denotes a cleaning-liquid supply pipe formed with jet orifices I0 directed towards the wheel I. ll denotes a debris pipe. l2 denotes the liquid to be filtered, and I3 denotes an outlet for the filtered liquid.

In practice, the liquid held in the interstices 2 of the sheets 6 and l maintains the sheet 8 immersed in liquid. Cleaning liquid jets issuing from the orifices I 0 can thus pass through the fine meshes in the sheet 8 Without encountering resistance from surface tension, the debris pipe ll receiving the soiled cleaning liquid. The motor l rotates the screen I by way of the friction wheel 5, thereby continually presenting a fresh part of the filtering screen to the cleaning fluid.

It is to be understood that in the drawing the size of the meshes is grossly exaggerated. For example the ultra-fine meshes of the sheet 9 may be of the order of 100,000 per square inch.

What is claimed is:

1. A filtering medium comprising an inner woven wire fabric sheet having interstices of microscopic size with the inherent property of preventing the passage of a liquid except when immersed therein, and an outer woven wire rabric sheet at each side of said inner sheet, the interstices of the outer sheet being relatively larger than the interstices of the inner sheet but sum cien-tly small that surface tension normally will maintain liquid in them, the outer sheet being sufilciently close to the inner sheet that when the outer sheets are wetted, surface tension of the wetting liquid will cause a body of the liquid to be maintained between the outer sheets so that the inner sheet will be maintained immersed in said body of liquid, whereby the microscopic interstices of the inner sheet are in fluid communication with the body of liquid on each side of the inner sheet and surface tension of the liquid will be ineffective to prevent passage of a cleaning liquid through said sheets.

2. A filterin medium as set forth in claim 1 in which the inner woven wire fabric sheet is of stainless steel. M

3. A filtering medium as set forth in claim 1 in which the interstices of the inner woven wire fabric sheet are of the order of 100,000 per square inch.

PERCIVAL LIONEL BOUCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain 1883 Number Number 

